Safety work and creation of a backup route for the Chambon Tunnel
2 November 2017
Underwater reconnaissance and expert survey of Marèges dam structures
2 November 2017

Blocking and refurbishment of bottom outlets on l’Hongrin dam

  • Country: Switzerland
  • Activity: Dams
  • Blocking and refurbishment of bottom outlets on l’Hongrin dam.

Summary: For the refurbishment of the safety controls on the bottom outlets of the l’Hongrin dam, Hydrokarst divers had to descend to a depth of 70 m to install two steel packers to block the outlets, each measuring 4 m in diameter and weighing 7.3 tonnes.

Despite the extreme weather conditions (temperatures descending to -25°C on the structure at 1255 m altitude), the choice of using a saturation diving system during winter enabled us to achieve two objectives: minimise the impact on production and avoid thermal problems on dam seals, which would occur if it had been emptied.  The installation of packers enabled us to refurbish the valves upstream in full safety.